Side Match I: Color

Inspectors probably are hired to inspect side match problems more frequently than any other category of complaint. It’s a broad subject covering lots of different, unrelated conditions.

Side match problems are tricky to diagnose correctly, but the fact that they’re so common makes getting it right especially important. Despite the diagnostic difficulties, getting it right is possible, so I’m devoting a four-part series to mastering the subject. I’ll cover actual color variations (hue and shade) here in Part I. Part II will discuss texture variations. Part III will cover pile direction issues. Finally, Part IV will describe the investigative tools and techniques you can use to get it right every time. At some point in the future I’ll talk about correction, but by the time we get to Part IV, I predict you’ll be plenty tired of this subject.

What is it?

Poor side match refers to a condition in which two cuts of carpet differ in color, texture or some other aspect of their appearance where they are seamed together.

C’mon, it doesn’t look that hard

Maybe that’s why it is. Side match claims are misdiagnosed because there are lots of conditions that look like color variance, but actually aren’t. That’s right—color can appear to differ even when it really doesn’t. To make matters worse, the conditions often occur in combinations and there may be different combinations of factors at every seam. The inspector must be able to differentiate among the factors contributing to the carpet’s appearance and confirm or rule out each one individually.

Doing that correctly is sometimes very, very hard. So hard, in fact, that the claims manager of one large mill confided that side match complaints are misdiagnosed by inspectors—certified inspectors—on about 50% of the cases he sees. Those are expensive mistakes. His estimate agrees with my experience doing re-inspections: The original diagnoses were at least incomplete, if not flat-out wrong, about half of the time. That’s how hard it is.

Part I: Color Variance

There are lots of models for expressing the various dimensions of color. The model that is most useful to this discussion is the HSV (aka HSB) model, which expresses a color as a combination of hue, saturation and value (brightness or shade). I’m not going to cover saturation in this article because, on its own, it’s rarely relevant to side match complaints; however, shade and hue are important, so I’ll discuss them here.

Shade Variations

“Shade” refers to the relative darkness or lightness of a color. Of the cases that actual are color variations, shade variations are by far the most common. (Figures 1, 2, 3.)

For the inspector, the problem is that several other conditions look exactly like shade variations, but aren’t. Real shade variations usually are visible (more or less) from all directions, but one feature to look for is that the shade difference does not reverse when you view it from different directions. That is, the side that appears darker when viewed from one direction does not appear lighter when viewed from the opposite direction. This is important, because there are other conditions that do reverse. (We’ll get to those later.)

Shade differences often are most distinct standing at one end of the seam with the pile lying toward you and a high-intensity light (1,000-watt or higher) directly over the seam.

Shade variation is the only type of side match defect with an actual industry standard to assess it against. The maximum allowable variance is a rating of 4-5 or better on the AATCC Gray Scale. The AATCC Gray Scale is a reference consisting of ten pairs of gray chips representing various degrees of shade difference. The pairs are rated from 5 (no difference) to 1 (severe change).

Note that “4-5″ is one specific rating value on the scale; it does not mean “between 4 and 5.” Where you would expect to find a rating called something more logical, like, say, “4.5,” the scientists who created the Gray Scale—and only they—thought a rating called “4-5″ made sense, and it’s been that way ever since.

You can order your very own Gray Scale from the AATCC.

The Gray Scale-based standard holds up pretty well with solid-colored carpet, but it falls apart when you’re dealing with patterned carpet. Does the 4-5 rating apply to each color individually or all the colors collectively? Well, there’s no real standard for that. In patterned carpet, and printed carpet in particular, the shade variance might occur in only one color of the pattern. If it’s the background color, it might be easy enough to pick out, but if it’s one of the accent colors, you might stare at the carpet for half an hour before you’re confident you’ve found the actual problem.

Peaked Seams

Peaked seams are the most common cause of misdiagnosed side match complaints. In fact, in residential cases, you’ll almost certainly find that the majority of side match claims you are called to inspect turn out to be nothing more than peaked seams, without any shade variance whatsoever. It’s impossible to overemphasize how convincingly a peaked seam can mimic shade variation. Your eyes will insist that there absolutely, positively must be a difference, even when there isn’t. (Figures 4, 6.)

Peaked seams resemble shade differences when they are lit primarily from one side, such as when a seam runs in front of a large window or sliding glass door. (Figure 5.) Like real shade differences, this condition is more or less visible from all directions and doesn’t reverse when viewed from different directions. However, three things distinguish it from real differences:

1. The perceived shade difference is strongest when you view the seam from the side opposite the dominant light source. The difference might not even be visible at all when you’re standing on the same side as the light with the light behind you.

2. With the side lighting removed, the apparent shade difference vanishes under high-intensity light.

3. A distinct bulge will be visible along the seam when you cast a shadow over the carpet by shining a bright light over the pile at a low angle.

With multiple windows, sometimes it’s hard to tell where the strongest light is coming from. An easy trick is to crease a piece of paper and lay it with the crease above the seam. Walk around it, and the darker edge of the seam will match the darker half of the paper. (Figure 7.)

Most seams in stretch-in installations will exhibit peaking to at least some degree, so it’s important to be able to distinguish peaking from real shade variations.

Hue Variations

“Hue” refers to the chroma of a color, the combination of wavelengths of light an object reflects (or emits) that makes it appear blue, green or red, for instance. (Figure 8.) An example of hue variation would be where two cuts of blue carpet are joined and one appears slightly more green, while the other appears slightly purple.

Like shade variations, hue variations are most visible with high-intensity lights directly over the seam and the pile lying toward you.

Hue variations are relatively rare. Within individual dye lots, they are exceptionally rare. When you do find actual hue variations, they almost always (but not absolutely always) indicate that the joined cuts are from different production lots. When you encounter hue variations, be alert to other signs of different production lots. Differences in backing materials, latex color or stitch rate are strong indicators that you’re looking at more than one lot.

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